There is considerable indirect evidence that relative mid-zone arterial wall hypoxia may be a potentiating factor in the development of atherosclerosis, particularly after smooth muscle hyperplasia has occurred, increasing diffusion distances. However, little is known about oxygen delivery or utilization even within the normal arterial wall. This project is designed to examine the factors involved in oxygen delivery to the arterial wall experimentally and analytically. Oxygen concentration profiles are obtained across the living, in situ, undeformed arterial wall using a microcathode. Such profiles have been used to examine the factors affecting the direction of diffusion, and with the choice of a suitable diffusion model, to calculate medial oxygen consumption. The experiment will be modified in the future to measure in vivo diffusion coefficient. The Navier-Stokes and diffusion equations have been programmed for numerical solution, to examine the possibility of interaction between secondary flow structure and oxygen availability. Initial results suggest a marked decrease in oxygen availability to the intima at the upstream edge of flow separation areas.